Yes, I still have my 2008 Mini 9, but the two batteries I had for it, the original Dell 4-cell and an aftermarket 8-cell, were dead. I recently ordered a replacement 4-cell battery from Amazon and it works great with BIOS A07, charging fine and giving normal run-times.
https://www.amazon.com/gp/product/B00WBH8FJI/
I saw other batteries there, some had poor reviews.